Study of amorphous nanocrystalline thin silicon films by grazing-incidence small-angle X-ray scattering

Abstract

Thin Si films, with thicknesses between 100 and 400 nm, were deposited by radio frequency plasma enhanced chemical vapour deposition in silane gas (SiH 4 ) highly diluted by hydrogen. The growing conditions were varied to obtain different degrees of crystal fractions and a variety in individual crystal sizes. The crystalline to amorphous volume fraction, as estimated by Raman spectroscopy, varied from 5 to 45% while the individual crystal sizes varied from 2 to 8 nm. The average density of the samples was estimated by using near infrared spectroscopy and the effective medium approximation. All samples were porous and contained void volume fraction between 15 and 25%. Grazing-incidence small-angle X-ray scattering has been performed at the ELETTRA synchrotron radiation source (Trieste, Italy). The scattering patterns of all examined samples indicate the presence of 'particles' in the 'bulk' of the thin films with gyration radii in the range of 2 to 5 nm. The higher values were found for the samples with a higher crystalline fraction. The size and the size distribution of 'particles' depend upon the deposition conditions. The samples which had been deposited with a higher discharge power and a lower silane fraction had larger particles and the roughness of their surface was higher.

Spectral and Morphological Studies of Nanocrystalline Silicon Thin Films Synthesized by PECVD for Solar Cells

“…For the purpose of this work, we used XRD and Rietveld refinement for estimation the crystal to amorphous fraction and crystal size. Raman spectroscopy (RS) is non-destructive, extensively employed technique for the structural analysis of completely amorphous or amorphous-nanocrystalline multicomponent silicon-based thin films [13,24,[29][30][31][32][33]. Since the interpretation of the Raman measurements largely influences the estimated structural data, RS has to be combined with other methods, typically microscopy or XRD.…”

Nanostructure of thin silicon films by combining HRTEM, XRD and Raman spectroscopy measurements and the implication to the optical properties

“…More details about growing conditions can be found in our previous papers [22,24]. As a rule, the higher the silane dilution, the larger the crystals and higher fraction of crystalline phase are obtained.…”

“…For the purpose of this work, we used XRD and Rietveld refinement for estimation the crystal to amorphous fraction and crystal size. Raman spectroscopy (RS) is non-destructive, extensively employed technique for structural analysis of completely amorphous or amorphous-nanocristalline multicomponent silicon-based thin films [4,15,[20][21][22][23][24]. Since the interpretation of the Raman measurements largely influences the estimated structural data, RS has to be combined with other methods, typically microscopy or XRD.…”

Spectral response of amorphous–nano-crystalline silicon thin films

“…The crystalline fraction and individual size of crystals increases with power density and silane dilution. More details abut the deposition conditions and theirs influence on nano-size properties are published elsewhere [4,7,8].…”